The incident occurred in the seventh minute, when Clark was apparently upset that the ball boy didn’t get him the ball faster for a throw-in. The slur was clearly audible on the national NBC Sports Network broadcast.

Clark, 27, said he was sorry for the explicit outburst shortly after the game on Twitter.

“I’d like to offer a sincere apology to everyone who watched the game, especially the ball boy for whom I used awful language towards,” he wrote in one post.

Most Read Stories

Clark, the 2009 Colorado Rapids’ Humanitarian of the Year, followed up with a second post: “I didn’t mean to disrespect anyone and am sorry for letting my emotions get the best of me. It’s not who I am, and it won’t happen again.”

MLS is conducting a review of the incident and “examining possible disciplinary action,” according to a statement from a league spokesman.

The Dynamo and Clark, an eight-year MLS veteran, will be cooperative in the process, the team said in its own statement.

“Colin is very remorseful for his actions, which were inappropriate and do not represent his true character,” part of the statement read. “He has issued a public apology and he will personally apologize to the ball boy.”

NBC Sports producers didn’t catch Clark’s slur on the live broadcast and would’ve issued an on-air apology had they heard it, according to a spokesman.

The Sounders declined to comment, deferring to the league on the matter.

There’s little precedent for punishment regarding this type of abuse, but in a somewhat related incident, Liverpool forward Luis Suarez was fined and suspended eight games by The Football Association of England for using a racial slur toward Manchester United defender Patrice Evra. That was directed at an opponent, however, and not a ball boy.

Last month, New England Revolution midfielder Lee Nguyen received backlash for using a gay slur on Twitter while with the Vancouver Whitecaps, but that was in a teasing manner toward a teammate. Nguyen was released by Vancouver a couple of weeks later, but club officials insisted it was a soccer decision, and he wasn’t formally punished.